Apparatus and method of backflow prevention

ABSTRACT

A backflow preventer apparatus comprising an inline solenoid valve configured to shut when de-energized, disposed between a closed system desired to be evacuated and a vacuum pump, wherein the inline solenoid valve and vacuum pump share a common source of electrical power.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent Application Ser. No. 61/898,657 filed Nov. 1, 2013. The entirety of the provisional application is incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure generally relates to backflow prevention. More specifically, the present disclosure relates to an inline valve configured to prevent backflow in a closed refrigeration system upon loss of vacuum.

BACKGROUND

Some closed systems, such as refrigeration systems, require initial evacuation of non-condensable gasses and other contaminants. In some situations, such systems will also require periodic evacuation to ensure continued efficient operation and longevity of the system. A vacuum pump is used to create and maintain a vacuum pressure on the system; this vacuum pressure is often maintained for extended durations—lasting several hours or even several days—to ensure complete system evacuation. The modern trend of creating larger and more complex refrigeration systems is only increasing the duration of system evacuations.

If electrical power is lost to the vacuum pump, or the vacuum pump fails, during the evacuation of a refrigeration system there is potential for backflow into the system as the system returns to ambient pressure. Such backflow is undesirable as it will re-introduce the non-condensable gasses and other contaminants which the evacuation process sought to remove. Depending on the strength of the vacuum and subsequent backflow, the oil of the vacuum pump may also be introduced into the refrigeration system causing additional problems. Such backflow also creates a potential hazard for the vacuum pump itself, as oil migration from the pump into the refrigeration system could cause the pump to seize. This condition requires that the pump and refrigeration system be properly re-set before continued operation or damage to the vacuum pump may occur.

Prior solutions to the problem of backflow during the evacuation of a refrigeration system include the use of a check valve in the suction line, positioned between the refrigeration system and the vacuum pump. However, check valves require a strong differential pressure to properly seat and seal in a vacuum. Air is a particularly poor medium for translating this pressure into a sealed check valve. Additionally, the differential pressure across a check valve during evacuation is often insufficient to seal the check valve once the vacuum pump is offline. For these reasons, a check valve fails to prevent system backflow during a loss of vacuum pump while evacuating a refrigeration system. Indeed, users of check valves have reported slowly decreasing vacuum pressures, indicating backflow is occurring in these situations.

SUMMARY OF THE DISCLOSURE

The present disclosure is directed to an apparatus and method of backflow prevention which generally obviates the deficiencies cited above. In one embodiment, the present disclosure relates to an inline solenoid back flow preventer valve connected between a refrigeration system desired to be evacuated and a vacuum pump. The inline solenoid valve shares a common electrical power source with the vacuum pump, such that a loss of power to the vacuum pump also causes a loss of power to the solenoid, which closes the back flow preventer valve during a loss of power condition. In another embodiment, the present disclosure further provides a method of installing and operating the inline solenoid valve, which comprises connecting a solenoid valve between a refrigeration system and a vacuum pump, energizing the solenoid valve's electrical end and the vacuum pump from a common electrical power source, and consistently providing electrical power to the solenoid valve's electrical end and the vacuum pump from a common electrical power source, causing the solenoid valve to remain open and the vacuum pump to remain operating and drawing a vacuum on the refrigeration system.

In another embodiment, the back flow preventer valve may be energized from a separate power source from the vacuum pump and includes a sensor to monitor the operation status of the vacuum pump. A relay may cause the backflow preventer valve to shut if the sensor determines a failure or de-energizing of the vacuum pump.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the present disclosure will become apparent upon reading the following detailed description and upon reference to the drawings.

FIG. 1 is a block diagram of a backflow preventer apparatus in accordance with some embodiments of the present disclosure.

FIG. 2 is a block diagram of a backflow preventer apparatus in accordance with some embodiments of the present disclosure.

FIG. 3 is a block diagram of a backflow preventer apparatus in accordance with some embodiments of the present disclosure.

FIG. 4 is a block diagram of a backflow preventer apparatus in accordance with some embodiments of the present disclosure.

FIG. 5 is a block diagram of a backflow preventer apparatus in accordance with some embodiments of the present disclosure.

FIG. 6 is a flow diagram of a method of testing the operation of a backflow prevention apparatus in accordance with some embodiments of the present disclosure.

While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the present disclosure is not intended to be limited to the particular forms disclosed. Rather, the present disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims.

DETAILED DESCRIPTION

Many systems utilized in industrial and commercial applications require a pressure-dependent directional flow environment to maintain efficient and effective operations. For example, refrigeration systems designed to operate in a moisture-free environment require an evacuation process that requires maintaining a vacuum for extended periods of time. Devices for cleaning such systems must create and maintain a specific desired vacuum pressure throughout the operation.

Specifically, refrigeration systems require a moisture- and contaminant-free environment to efficiently operate. Removal of air and other non-condensable gasses is known as degassing and removal of moisture is known as dehydration. The process of removing non-condensable gasses, moisture, and other contaminants is typically referred to as evacuation. The evacuation process is periodically or occasionally necessary to ensure the continued efficient operation of a refrigeration system.

During the evacuation process, pressure is reduced using a vacuum pump to lower the boiling point of non-condensable gasses in order to remove them from the system. If non-condensable gasses such as air are not removed, the system will operate at higher than normal condensing pressures. This happens because the air is trapped at the top of the condenser and will not condense, effectively reducing the condenser capacity and reducing condenser efficiency because the refrigerant has a smaller volume with which it will change its state from a vapor to a liquid. Increasing the condensing pressure results in higher compression ratios and higher discharge temperatures, both of which can decrease efficiency and reliability of the refrigeration system.

The evacuation process also serves the purpose of removing water vapor from the system. Very small amounts of water present in a refrigeration system combine with heat and refrigerant to form acids. Acids mix with oil and metal parts within the system to form sludge which can clog and damage the refrigeration unit. Alternatively, the water vapor may freeze during operation of the refrigeration system, creating another potential obstruction in the system and further reducing system efficiency.

Evacuation is achieved by installing a suction line, for example in the form of a refrigeration hose, to the system and attaching a vacuum pump, which is also referred to as an evacuation pump. A vacuum atmosphere is required since moisture can only be removed from a system in vapor form. Consequently, a completely sealed evacuation environment is necessary to establish a deep vacuum and perform the evacuation.

Several factors influence the “pumping speed” of a vacuum pump, and thus the time required to remove all moisture from a refrigeration system. Some of the most important are: the cubic feet of the refrigeration system; the amount of moisture contained within the refrigeration system; the ambient temperature present; internal restrictions within the refrigeration system; external restrictions between the refrigeration system and the vacuum pump; and the size of the vacuum pump. Ultimately, maintaining an operational vacuum pump for the duration of the evacuation process is absolutely critical to successfully evacuating a refrigeration system.

During the evacuation of a refrigeration system a loss of power to the vacuum pump creates the potential for backflow into the system as the system returns to ambient pressure. Such backflow is undesirable as it is likely to re-introduce the non-condensable gasses and other contaminants which the evacuation process sought to remove. Once this occurs, the evacuation process must be recommenced. Such backflow also creates a potential hazard for the vacuum pump itself, as oil migration from the pump into the refrigeration system could cause the pump to seize. This condition requires that the vacuum pump and refrigeration system be properly re-set before continued operation or damage to the vacuum pump may occur.

In one embodiment, the present disclosure provides a solution to the problem of re-contamination of a partially-evacuated refrigeration systems due to loss of power at the vacuum pump. The present disclosure may reasonably be applied to other fields and endeavors with equal success.

FIG. 1 is a block diagram of a backflow preventer apparatus 100 in accordance with some embodiments of the present disclosure. A refrigeration system 10 which is desired to be evacuated may be connected to a vacuum pump 16 via a first hose 15. In one embodiment, vacuum pump 16 has a built-in solenoid valve 12, comprising a solenoid valve end 14 and a solenoid electrical end 13, attached to the suction connection 17 or suction manifold of the vacuum pump 16. Solenoid valve 12 and vacuum pump 16 receive electrical power from power source 18. In another embodiment, vacuum pump 16 and solenoid valve 12 may be separate with the solenoid valve 12 located in the first hose 15 on the suction path side of the vacuum pump 16.

First hose 15 may be connected to refrigeration system 10 via a service port 20 on refrigeration system 10. In some embodiments, first hose 15 is a ¼ inch charging hose rated for 800 psi working pressure and 4,000 psi burst pressure. In some embodiment, ¼ inch brass refrigeration fittings are used to connect first hose 15 to refrigeration system 10 and solenoid valve end 14.

In one embodiment, solenoid valve 12 is configured to fail shut; that is, the solenoid valve end 14 will remain shut unless solenoid electrical end 13 is energized. When solenoid electrical end 13 is de-energized, solenoid valve end 14 is shut. In some embodiments, the solenoid electrical end 13 is a MKC-1 coil by the Sporlan Division of Parker Hannifin Corporation. In some embodiments, the solenoid valve end 14 is a W3 valve also by the Sporlan Division of Parker Hannifin Corporation. In some embodiments, solenoid valve end 14 comprises a gate, ball, globe, or similar mechanical or pneumatic valve which is operated (i.e. opened and shut) by solenoid electrical end 13.

In one embodiment, solenoid valve 12 and vacuum pump 16 share a common electrical power source 18. In some embodiments, this is implemented by connecting a standard 3-prong, 110V power cord for powering the solenoid electrical end 13 in parallel with a standard 3-prong, 110V power cord for powering the vacuum pump 16. Connection in parallel can be achieved by connecting the power cord for the solenoid electrical end 13 and the power cord for the vacuum pump 16 to the same electrical outlet, or by employing an electrical power ‘splitter’ which takes a single power input and divides it into parallel power outputs. In some embodiments, power source 18 is a portable generator or similar mobile electrical power generating device.

In some embodiments, electrical power is supplied to solenoid electrical end 13 via vacuum pump 16 rather than independent of vacuum pump 16. Put another way, electrical power runs from power source 18 to vacuum pump 16 and then to solenoid electrical end 13. In this embodiment, the effect remains that a loss of power to the vacuum pump 16 results in a loss of power to the solenoid electrical end 13, causing solenoid valve end 14 to shut.

In some embodiments, such as that illustrated in FIG. 4 and discussed below, electrical power is supplied to solenoid valve 12 and vacuum pump 16 from two independent power sources.

In some embodiments, additional instrumentation such as a pressure gage is provided on either side of the solenoid valve, or on the service connection of refrigeration system 10 or on the vacuum pump 16, to enable a user to verify solenoid valve 12 is open based on an equivalent pressure on either side of solenoid valve 12 and to verify that a desired vacuum pressure has been achieved. In some embodiments, a differential pressure gage is provided to measure the pressure difference across the solenoid valve 12. Differential pressure gage can be connected from first hose 15 to second hose 22, from refrigeration system 10 to suction connection 17, or in any other suitable configuration to measure the pressure difference across the solenoid valve 12.

In some embodiments, an alarm (not shown) is operably connected between the electrical power source 18 and vacuum pump 16, between the electrical power source 18 and solenoid electrical end 13, or both. The alarm is configured to alarm—aurally or visually—during a loss of power or interruption of power at the electrical power source 18.

Vacuum pump 16 may discharge the exhaust from refrigeration system 10 evacuation to the surrounding atmosphere 19. However, in some embodiments, additional connections can be made to discharge the evacuation exhaust to a holding tank, sequestered area, or other volume. For example, in some embodiments the vacuum pump 16 exhaust may be directed via additional hoses to an on-site storage tank.

In one embodiment, in operation, solenoid electrical end 13 and vacuum pump 16 are energized from power source 18, causing solenoid valve end 14 to open and vacuum pump 16 to begin drawing a vacuum. So long as electrical power is consistently available solenoid electrical end 13 will remain energized, solenoid valve end 14 will remain open, and vacuum pump 16 will remain operating and drawing a vacuum on refrigeration system 10. However, in the event of a loss of electrical power the solenoid electrical end 13 and vacuum pump 16 de-energize. When solenoid electrical end 13 de-energizes, solenoid valve end 14 shuts, locking in vacuum pressure on the refrigeration system 10 and preventing the refrigeration system from returning to ambient pressure.

In the event of an interruption of electrical power rather than a loss of electrical power (i.e.—a temporary loss of electrical power followed by the restoration of electrical power), solenoid electrical end 13 and vacuum pump 16 are re-energized when electrical power is restored. Solenoid valve end 12 is re-opened and the evacuation continues.

In some embodiments, such as that illustrated in FIG. 5, a switch 51 is used to prevent re-energizing solenoid valve 12 and vacuum pump 16 once power is restored following an unexpected loss of power. Switch 51 is configured to be shut manually (i.e. by human action) and to open upon a loss of electrical power. Thus once power is restored, solenoid valve 12 will not open and vacuum pump 16 will not resume pumping until manual intervention. Switch 51 therefore ensures proper oversight of the restart operation and prevents potential damage to vacuum pump 16.

FIG. 2 is a block diagram of a backflow preventer apparatus 200 in accordance with some embodiments of the present disclosure. A refrigeration system 10 which is desired to be evacuated may be connected to a solenoid valve 12 via a first hose 15. A second hose 22 may connect the suction connection 17 of vacuum pump 16 to solenoid valve 12, which is disposed between refrigeration system 10 and vacuum pump 16. Solenoid valve 12 comprises a solenoid valve end 14 and a solenoid electrical end 13. Solenoid valve 12 and vacuum pump 16 may receive electrical power from power source 18.

FIG. 3 is a schematic diagram of a backflow preventer apparatus 300 in accordance with some embodiments of the present disclosure. A refrigeration system 10 which is desired to be evacuated may be connected to a solenoid valve 12 via a first hose 15. A second hose 22 may connect the suction connection 17 of vacuum pump 16 to solenoid valve 12, which is disposed between refrigeration system 10 and vacuum pump 16. Solenoid valve 12 comprises a solenoid valve end 14 and a solenoid electrical end 13. Solenoid valve 12 and vacuum pump 16 receive electrical power from power source 18. FIG. 3 illustrates those embodiments of the present disclosure which employ an electrical power ‘splitter’ to simultaneously and in parallel supply electrical power to solenoid electrical end 13 and vacuum pump 16.

In another embodiment, illustrated in FIG. 4, solenoid valve 12 and vacuum pump 16 are independently powered. Solenoid electrical end 13 receives electrical power from first power source 42 and vacuum pump 16 receives electrical power from a second power source 44. A sensor may be used to monitor the condition of the vacuum pump 16. In one embodiment, the sensor may measure the vacuum pressure on the suction side of the vacuum pump 16. In another embodiment, the sensor may measure the differential pressure across the vacuum pump 16. In yet another embodiment, the sensor may measure the electrical current applied to the vacuum pump 16, for example by using a current sensing relay in the electrical connection between the power source 44 and vacuum pump 16. The sensor may operationally connect to an relay 46 that supplies or interrupts electrical power to the solenoid electrical end 13. The various potential inputs to relay 46, described above, are illustrated in FIG. 4 by dashed lines.

If the sensor senses a condition that the vacuum pump 16 is not operating properly, the sensor triggers the relay 46 to remove power to the solenoid electrical end 13 thereby shutting solenoid valve end 12 and preventing backflow. In some embodiments, relay 46 is biased to remove power to solenoid electrical end 13 thereby shutting solenoid valve end 12 before the vacuum pump 16 has fully ceased pumping. For example, relay 46 can be set to remove power to solenoid electrical end 13 at a measured vacuum pump 16 suction pressure which indicates a possible problem with vacuum pump 16 but not necessarily a failure of vacuum pump 16.

In further embodiments, a relay 46 may be configured to interrupt power to the vacuum pump 16. In this configuration, relay 46 would receive input from the solenoid electrical end 13 to determine when solenoid valve 12 had lost power and was therefore shut. In such embodiments, the relay 46 is used to remove power from the vacuum pump 16 upon closure of the solenoid valve 12, to prevent any, or further, damage to the vacuum pump 16.

A method of backflow prevention is further provided by the present disclosure. In one embodiment, in a first step, solenoid valve 12 is connected between refrigeration system 10 and vacuum pump 16. In a second step, solenoid electrical end 13 and vacuum pump 16 are energized from power source 18, causing solenoid valve end 14 to open and vacuum pump 16 to begin drawing a vacuum. In some embodiments, additional instrumentation such as a pressure gage is provided on either side of the solenoid valve, or on the service connection of refrigeration system 10 or on the vacuum pump 16, to enable a user to verify solenoid valve 12 is open based on an equivalent pressure on either side of solenoid valve 12. In a third step, electrical power is consistently provided to solenoid electrical end 13 and vacuum pump 16, causing solenoid valve end 14 to remain open and vacuum pump 16 to remain operating and drawing a vacuum on refrigeration system 10.

In another embodiment, illustrated at FIG. 6, a method 600 of testing the operation of a backflow prevention apparatus is also provided in the present disclosure. Method 600 starts at block 601. In a first step 602, solenoid valve 12 is connected between refrigeration system 10 and vacuum pump 16. In a second step 603, solenoid electrical end 13 and vacuum pump 16 are energized from power source 18, causing solenoid valve end 14 to open and vacuum pump 16 to begin drawing a vacuum (block 604). At block 605, electrical power is secured to solenoid electrical end 13 and vacuum pump 16, causing solenoid electrical end 13 to de-energize, solenoid valve end 14 to shut, vacuum pressure on the refrigeration system 10 to become locked in, and preventing the refrigeration system from returning to ambient pressure. In some embodiments, instrumentation such as a pressure gage is connected to the vacuum side of solenoid valve 12 (i.e.—the side including refrigeration system 10 and first hose 15) to enable a user to verify vacuum pressure is maintained in refrigeration system after the loss of power. Such system monitoring comprises block 606. In some embodiments, periodic monitoring of the vacuum pressure in the refrigeration system 10 during the loss of electrical power condition evaluates whether the system is losing vacuum. A steady loss of vacuum pressure could indicate backflow into refrigeration system 10. Method 600 ends at block 607.

The present disclosure provides numerous advantages over the prior art. Most notably, the present disclosure provides a means of positive closure to lock in vacuum pressure following a loss of the vacuum pump. This ability was lacking in prior art, particularly the use of check valves, to prevent backflow. The present disclosure also links performance of the solenoid valve with the performance of the vacuum pump—either by a common electrical power source or by sensing means—to ensure these components work in tandem. Additionally, the present disclosure provides significant savings in time and money during a loss of vacuum pump while evacuating because the vacuum pressure is locked in, backflow into the refrigeration system is prevented, and the need to reset the vacuum pump may be obviated.

Although the present disclosure is directed to the evacuation of a refrigeration system, the apparatus and method disclosed herein can be applied to various additional closed systems which require the application of vacuum pressure. The term ‘refrigeration system,’ as used to describe the various embodiments, should not be read as limiting the present disclosure in any way.

It may be emphasized that the above-described embodiments, particularly any “preferred” embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiments of the disclosure without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this.

While this specification contains many specifics, these should not be construed as limitations on the scope of any disclosures, but rather as descriptions of features that may be specific to particular embodiment. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments. 

What is claimed is:
 1. An apparatus for preventing backflow during the evacuation of a refrigeration system, comprising: a vacuum pump having a suction connection end and a discharge end configured to discharge to an atmosphere; a solenoid valve having a solenoid valve end and a solenoid electrical end, wherein the solenoid valve end is operably connected to the suction connection end of the vacuum pump and is operably connected by a first hose to a refrigeration system desired to be evacuated, and wherein the solenoid valve is normally shut and energized open when electrical power is supplied to the solenoid electrical end; and an electrical power source operably connected to the vacuum pump and solenoid electrical end, wherein a loss of electrical power at the electrical power source or an interruption of electrical power to the vacuum pump and solenoid electrical end thereby results in the shutting of the solenoid valve and securing of the vacuum pump thereby preventing backflow from the atmosphere and the vacuum pump into the refrigeration system.
 2. The apparatus of claim 1, wherein the first hose is connected to the refrigeration system via a service port.
 3. The apparatus of claim 2, further comprising an alarm operably connected to the electrical power source and configured to alarm during a loss or interruption of electrical power to the solenoid electrical end and vacuum pump.
 4. The apparatus of claim 3, further comprising a switch disposed between the electrical power source and the vacuum pump, wherein the switch is configured to open on loss of electrical power and requires manual action to shut thereby preventing inadvertent re-starting of the vacuum pump.
 5. A backflow preventer apparatus, comprising: a vacuum pump having a suction connection end and a discharge end; a solenoid valve having a solenoid valve end and a solenoid electrical end, wherein the solenoid valve end is operably connected to the suction connection end of the vacuum pump, and wherein the solenoid valve is normally shut and energized open when electrical power is supplied to the solenoid electrical end; at least one electrical power source operably connected to the vacuum pump and solenoid electrical end; a relay configured to selectably interrupt electrical power to the solenoid electrical end, wherein the relay is responsive to an operating condition of the vacuum pump; and a first hose operably connecting the solenoid valve end to a refrigeration system wherein when the solenoid valve is closed, backflow from the refrigeration system is prevented.
 6. The backflow preventer apparatus of claim 5, wherein the at least one electrical power source is a single electrical power source common to the solenoid valve and vacuum pump.
 7. The backflow preventer apparatus of claim 6, wherein the first hose is connected to the refrigeration system via a service port.
 8. The backflow preventer apparatus of claim 7, wherein the first hose is a 0.25 inch charging hose rated for 800 psi working pressure and 4,000 psi burst pressure.
 9. The backflow preventer apparatus of claim 7, wherein the relay is responsive to a loss of electrical power to the vacuum pump to thereby interrupt electrical power to the solenoid electrical end.
 10. The backflow preventer apparatus of claim 9 wherein the relay is configured to interrupt electrical power to the solenoid electrical end before all power is lost to the vacuum pump.
 11. The backflow preventer apparatus of claim 7, wherein the relay is responsive to a suction pressure of the vacuum pump failing to meet a predetermined threshold.
 12. The backflow preventer apparatus of claim 7, wherein the relay is responsive to a differential pressure across the vacuum pump failing to meet a predetermined threshold.
 13. The backflow preventer apparatus of claim 7, further comprising a switch configured to open on loss of electrical power and requiring manual action to shut.
 14. The backflow preventer apparatus of claim 5, wherein the at least one electrical power source comprises two independent electrical power sources, with a first electrical power source supplying electrical power to the vacuum pump and a second electrical power source supplying electrical power to the solenoid electrical end.
 15. The backflow preventer apparatus of claim 5, wherein a pressure gage is attached at least at one of between the refrigeration system and the solenoid valve, on a service connection of the refrigeration system, or to the suction end or discharge end of the vacuum pump.
 16. The backflow preventer apparatus of claim 5, further comprising a differential pressure gage operably connected to measure pressure across at least one of the solenoid valve or the vacuum pump.
 17. The backflow preventer apparatus of claim 5, wherein the evacuation end of the vacuum pump discharges to at least one of an atmosphere or a storage device.
 18. A backflow preventer apparatus, comprising: a vacuum pump, having a first side of a mechanical end of a solenoid valve integrally connected to a suction manifold of the vacuum pump and an electrical end of the solenoid valve connected to an integrated electrical power source, wherein the integrated electrical power source supplies power to the vacuum pump and the electrical end of the solenoid valve, and wherein the solenoid valve is normally shut and energized open when electrical power is supplied to the solenoid electrical end; a first pneumatic hose having a first end operably connected to a second side of the mechanical end of the solenoid valve and a second end operably connected to a service port of a refrigeration system; a switch, connected between the integrated electrical power source and the vacuum pump and the solenoid valve, configured to open on a loss of power and require manual shutting following restoration of power.
 19. The backflow preventer apparatus of claim 18, further comprising a differential pressure gage operably connected to measure pressure across the integrally connected mechanical end of the solenoid valve and the vacuum pump.
 20. The backflow preventer apparatus of claim 18, wherein the vacuum pump further comprises an evacuation end which discharges to at least one of an atmosphere or a storage device. 